Expression of HLA-G in the retinal pigment epithelial cell line, ARPE-19

Abstract

 

Purpose

 

The nonclassical human leukocyte antigen (HLA) molecule, HLA-G, regulates the immune system and is important for immunological tolerance during pregnancy. HLA-G mediates the inhibition of the maternal immune response, which is instrumental in protecting the semi-allogeneic fetus, thus allowing a successful pregnancy. Furthermore, HLA-G inhibits NK and T cell cytotoxicity, T cell proliferation, and antigen presentation, and is involved in cancer, transplantation and a number of autoimmune and inflammatory diseases. NK cells have been described in the subretinal lesions of patients with age-related macular degeneration (AMD) and are believed to contribute to the pathogenesis of AMD. Since HLA-G inhibits NK cells, its expression by RPE cells might be of significance to AMD. The purpose of this study is to investigate the expression of HLA-G in RPE cells in vitro and to determine its regulation in response to proinflammatory cytokines.

 

Methods

 

As an inflammatory model, ARPE -19 cells were cultured and stimulated with IFN-γ and/or TNF-α. Gene expression analysis was performed by whole-transcriptome microarray. Protein expression was quantified by western blot and immunocytochemistry.

 

Results

 

Gene expression analyses of RPE cells show that HLA-G is constitutively expressed at a high level. Furthermore, the expression is up regulated when the cells are stimulated with IFN-γ and/or TNF-α. The results from protein analyses confirm these results on the protein level.

 

Conclusions

 

HLA-G is constitutively expressed in RPE cells in vitro. This expression is up regulated by proinflammatory cytokines and may be a part of the immune privilege of the posterior segment of the eye. HLA-G can inhibit NK cell and T cell mediated cytotoxicity, and can furthermore turn these effector cells into regulatory cells. Thus this molecule is an important immune modulator, and expression by the RPE cells may indicate a role for HLA-G in ocular diseases mediated by inflammation.

 

 

Microarray data from the RPE cell line, ARPE-19, show that HLA-G is constitutively expressed at a high level. The expression is increased when the cells are stimulated with IFN-γ and/or TNF-α.

 

 

A) Western Blot showing HLA-G protein expression. Expression is up regulated after stimulation with INF-γ and /or TNF-α. B) Protein expression is confirmed by immunofluorescence confocal microscopy.

 

Keywords: 701 retinal pigment epithelium • 555 immunomodulation/immunoregulation • 553 immune tolerance/privilege